This proposal deals with 1) the role of hexose in the regulation of morphogenesis and 2) the role of hexose in the regulation of pyruvate kinase isozyme in the dimorphic fungus, Mucor racemosus. It is significant that both isozymes of pyruvate kinase can be produced by one morphological type, a condition which has not been satisfied in other eucaryotic systems where isozyme relationships have been studied. It is also important to note that the expression of the two isozymes is controlled by media components with the result that only one form is generally found in the cell at a given time. Likewise the morphological transitions of Mucor racemosus can be completely controlled in a chemically defined medium by several different manipulations. The goals of this study are twofold: a) to determine the effect of hexose on the amount and total number of proteins produced by the cell during the morphological transitions, b) to determine the level(s) of control exerted by hexose on the type and activity of the pyruvate kinase in Mucor. Therefore this proposal deals with studies of the total cell protein content with techniques which allow separation and analysis of total number of proteins in the cell. In addition, the physical, chemical and kinetic characteristics of each purified isozyme of pyruvate kinase will be determined along with the role of macromolecular synthesis in the control of isozyme production and activity.